.TH std::vector::capacity 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::vector::capacity \- std::vector::capacity

.SH Synopsis
   size_type capacity() const;  (noexcept since C++11)
                                (constexpr since C++20)

   Returns the number of elements that the container has currently allocated space for.

.SH Parameters

   \fI(none)\fP

.SH Return value

   Capacity of the currently allocated storage.

.SH Complexity

   Constant.

.SH Example


// Run this code

 #include <iomanip>
 #include <iostream>
 #include <vector>

 int main()
 {
     int sz = 100;
     std::vector<int> v;

     auto cap = v.capacity();
     std::cout << "Initial size: " << v.size() << ", capacity: " << cap << '\\n';

     std::cout << "\\nDemonstrate the capacity's growth policy."
                  "\\nSize:  Capacity:  Ratio:\\n" << std::left;
     while (sz-- > 0)
     {
         v.push_back(sz);
         if (cap != v.capacity())
         {
             std::cout << std::setw( 7) << v.size()
                       << std::setw(11) << v.capacity()
                       << std::setw(10) << v.capacity() / static_cast<float>(cap) << '\\n';
             cap = v.capacity();
         }
     }

     std::cout << "\\nFinal size: " << v.size() << ", capacity: " << v.capacity() << '\\n';
 }

.SH Possible output:

 Initial size: 0, capacity: 0

 Demonstrate the capacity's growth policy.
 Size:  Capacity:  Ratio:
 1      1          inf
 2      2          2
 3      4          2
 5      8          2
 9      16         2
 17     32         2
 33     64         2
 65     128        2

 Final size: 100, capacity: 128

.SH See also

   size    returns the number of elements
           \fI(public member function)\fP
   reserve reserves storage
           \fI(public member function)\fP
